Investigations are underway regarding aspects of SLE in the NZB, NZB x NZW, MRL, and BXSB mouse models, as well as in humans. In vitro studies of the cellular mechanism of generation of anti-Sm, rheumatoid factor, and antibody to autologous erythrocytes are being pursued. Efforts are being made to determine the heterogeneity of anti-Sm in mice and humans. The role of anti-idiotypic antibody is being evaluated. Studies are being performed to ascertain the nature of the immune complexes deposited in the kidneys of MRL and BXSB mice.